The human eye can bring objects into focus because of its lens ability to accommodate. The lens is built of layers of sells. Neatly arranged, the layers allow light to pass through without scattering. Seventy fingerlike ligaments collectively known as the ciliary zonule holds the lens in place. The fibrous ligaments, in turn, are attached to the choroid coat by the circular ciliary muscle. When the zonule pulls the perimeter of the lens, the lens stretches into a flattened shape. This posture, the resting position of the eye, requires no adjustment to bring objects more than twenty feet away into focus. For the eye to focus an object within twenty feet, the ciliary muscle contracts, relaxing the zonule's pull and allowing the lens to bulge. The nearer an object, the more the lens assumes its rounded, balloon shape. But within six or seven inches, an object reaches the "near point", beyond which the lens cannot accommodate enough to focus.
In order to support the accommodation ability of an eye within the range of 0.5-20 feet, the ciliary muscle should preserve its ability of contraction. And ciliary muscle deteriorates when not in use as well as any other muscle group in the human body. In other words, the ciliary muscle needs permanent training. Being regularly focused within the same distance from an object during a long time periods (when reading, watching TV, looking at the computer screen, and alike), the eye looses its ability to properly accommodate meaning a deterioration of ciliary muscle and a loss of acuity. Because changing of contemporary activities is unrealistic, the acuity therapy is needed. It is needed when a loss of acuity already takes place to prevent further deterioration and, depending on person's age, to fully or partly restore the acuity. It is also needed as a prophylaxis to prevent forming a hardened core (when shape of the eye lens does not change often enough) of mentioned above layers of cells that decrease accommodation. It is also needed to improve additional visual abilities, such as fixation on objects, maintaining attention for periods of time, judging relative distances of objects accurately, reading rapidly.
Methods and apparatus for increasing visual acuity are known. For example, Balliet (U.S. Pat. No. 4,408,846, Cl. 351/203) teaches a unit wherein a target is selectively moved toward or away from a person to different positions at accurately determined distances therefrom. At each of the positions, the person is required to identify the appearance of the target which is randomly changed to any one of a plurality of different appearances. The concept includes the moving of the target further away from the person whenever the identification of the target appearance is correct at a given position and moving the target closer to the person whenever the identification is incorrect. The system is adapted for increasing the far-point acuity of a myopic person, as well as increasing the visual acuity of an ametropic person. The system implies use of an optical bench wherein the target is carried, having means for incremental moving the support of the target toward or away from the person.
As one can see from the above description of the known system, it affects the visual acuity in the short range of distances about the far-point and the near-point. The system does not design for training the visual acuity in the whole range of 0.5-20' where shape of the eye lens is changing. The system also needs performing measurements and adjustments using the optical bench type equipment.
Systems where the target can be located at any distance from the person are also known. For example, O'Brien and Diamond (U.S. Pat. No. 4,726,672, Cl. 351/203) teach an exercise devise for improving poor visual acuity in which a person must identify randomly chosen figures of minimal visual stimulus. The system includes a solitary visual target, a means for randomly selecting and generating a number of various figures to be displayed on said visual target, a keyboard through which the person can respond to the figures seen on the visual target, and a means for informing the person of the correctness or incorrectness of said response. In the system means are provided for adjusting the apparent size of the displayed figure to maintain the figure displayed at a level of minimal discernable size.
The use of the system includes causing the target to randomly display at least one of a number of predetermined characters, providing the person with keyboard means to denote any of said characters, and comparing the character denote through the keyboard with the displayed character to detect and signify whether they coincide with each other. Then the apparent size of the displayed character is adjusted to maintain it at a level of minimal discernable size.
As it is indicated in the patent, it particular concern is the eye condition of amblyopia employing a hypothesis of minimal optical stimulation. The system to be operated in a darkened room or chamber. A pair of headphone speakers should be used to provide aid in the isolation of the person. The main intention is to provide an alternative to the use of so-called "patch therapy" which involves covering the non-affected eye of the person and forcing the person to function using only the affected eye.
One can see that the teaching is concerned mainly by the condition of amblyopia. The singular target can be located anywhere including the range of 0.5'-20', but in only one place at a time. Because of this condition the training of visual acuity can not be provided (and does not intend to) simultaneously in the whole range.
It is desirable for the acuity therapy apparatus and method to provide eye lens muscles training under the conditions so close to the natural eye environment as possible. In other words it is desirable to train eyes within the whole range of the lens contraction, where the targets are located as close to the person as 0.5' and as far as 20', and in between at a time. It is also desirable that the person could focus his or her eyes on targets located on different distances and appeared in a random order, exactly alike the natural conditions. It is further desirable for enhancing ciliary muscle training to stimulate the person to be concentrated on a target until the target information is correctly read, and only after that to go to another target. It is also desirable for the person to read the target characters at a level of minimal discernable size. It is desirable for the apparatus and method to provide general acuity therapy including conditions before any eye deterioration takes place. It is also desirable to provide the therapeutic value in a simple, inexpensive and fully portable apparatus that could be easily used by anyone and when in use does not require any special conditions such as darkened room or chamber, measurements, eye patch, and so forth.